Native Folders may be one of the more useful features of the upcoming Windows Phone 8.1 GDR1 update, but Phone Cover Apps is also high on the list. It promises smartphones accompanied by smart covers from Windows Phone OEMs.

Similar to what vendors like HTC, LG and Samsung have released for their Android handsets.

As this report details, Windows Phone 8.1 GDR1 will be able to detect when a cover has been attached to a smartphone, and it will also know when the cover is closed.

Whenever this happens, the operating system will automatically launch the Phone Cover App that the hardware vendors has preloaded on the device — thereby providing users with new options, features and additional capabilities.

A selection from the documentation Microsoft has put up for manufacturers:

“OEMs can build and register a phone cover app, which allows partners to create a user experience with their Windows Phones phone cover accessories. This application must be preloaded on the phone as a Settings/CPL application.

Moreover, OEMs will be able not only to set the app to be launched when the phone cover is closed, but also to come up with default settings for the lock screen’s auto unlock.”

Windows Phone 8.1 GDR1 will automatically detect whenever the cover is open, and will either unlock the handset, or prompt for a password.

And when it detects the cover is closed, it will lock the phone and launch the Phone Cover App in the foreground, which will be displayed above the lock screen, as you would expect.

However, details on what functionality Phone Cover applications will provide remain in the dark for now, but you can probably tick off the basic options like time, date, notifications, and all that. Chances are, manufacturers will be free to add the features they want.